关键代码：
<class-cache usage="read-write" class="com.shuoeasy.test.User"/> <!-- 集合级别的二级缓存，写法：包名.类名.字段名 --> <collection-cache usage="read-write" collection="com.shuoeasy.test.User.orders"/> <class-cache usage="read-write" class="com.shuoeasy.test.Orders"/>
或者代替hibernate.cfg.xml:<collection-cache usage="read-write" collection="com.shuoeasy.test.User.orders"/>
<cache usage="read-write"/>
代码片段：
User.java：
package com.shuoeasy.test;
import java.util.HashSet;
import java.util.Set;
public class User {
private int id;
private String userName;
private Set<Orders> orders = new HashSet<>();
public User() {
}
public User(String userName) {
super();
this.userName = userName;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public Set<Orders> getOrders() {
return orders;
}
public void setOrders(Set<Orders> orders) {
this.orders = orders;
}
@Override
public String toString() {
return "User [id=" + id + ", userName=" + userName + "]";
}
}User.hbm.xml：
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <!-- Generated 2016-6-25 14:50:51 by Hibernate Tools 3.4.0.CR1 --> <hibernate-mapping> <class name="com.shuoeasy.test.User" table="USER" > <id name="id" type="int"> <column name="ID" /> <!-- 指定主键的生成方式，native：使用数据库本地方式 --> <generator class="native" /> </id> <property name="userName" type="java.lang.String"> <column name="USERNAME" /> </property> <set name="orders" table="ORDERS" inverse="true" batch-size="100"> <!-- 可以在这里配置缓存，代替hibernate.cfg.xml:<collection-cache usage="read-write" collection="com.shuoeasy.test.User.orders"/> --> <cache usage="read-write"/> <key column="USER_ID"></key> <one-to-many class="com.shuoeasy.test.Orders"/> </set> </class> </hibernate-mapping>
Orders.java：
package com.shuoeasy.test;
public class Orders {
private int id;
private User user;
private String title;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
@Override
public String toString() {
return "Order [id=" + id + ", user=" + user + ", title=" + title + "]";
}
}Orders.hbm.xml：
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <!-- Generated 2016-6-25 14:50:51 by Hibernate Tools 3.4.0.CR1 --> <hibernate-mapping package="com.shuoeasy.test"> <class name="Orders" table="Orders"> <id name="id" type="int"> <column name="ID" /> <!-- 指定主键的生成方式，native：使用数据库本地方式 --> <generator class="native" /> </id> <property name="title" type="java.lang.String"> <column name="TITLE" /> </property> <many-to-one name="user" class="User" column="USER_ID"> </many-to-one> </class> </hibernate-mapping>
hibernate.cfg.xml：
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <!-- 连接数据库的基本信息 --> <property name="hibernate.connection.username">root</property> <property name="hibernate.connection.password">111111</property> <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property> <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8&useSSL=false&useLegacyDatetimeCode=false&serverTimezone=Australia/Melbourne&</property> <!-- hibernate 的基本信息 --> <!-- hibernate 所使用的数据库方言 --> <property name="hibernate.dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property> <!-- 执行操作时是否在控制台打印sql --> <property name="show_sql">true</property> <!-- 是否对sql进行格式化 --> <property name="format_sql">true</property> <!-- 指定自动生成数据表策略 --> <property name="hbm2ddl.auto">update</property> <!-- 启用二级缓存 --> <property name="cache.use_second_level_cache">true</property> <!-- 配置使用的二级缓存产品 --> <property name="hibernate.cache.region.factory_class">org.hibernate.cache.ehcache.EhCacheRegionFactory</property> <!-- 指定关联的 .hbm.xml文件 --> <mapping resource="com/shuoeasy/test/User.hbm.xml" /> <mapping resource="com/shuoeasy/test/Orders.hbm.xml" /> <class-cache usage="read-write" class="com.shuoeasy.test.User"/> <!-- 集合级别的二级缓存，写法：包名.类名.字段名 --> <collection-cache usage="read-write" collection="com.shuoeasy.test.User.orders"/> <class-cache usage="read-write" class="com.shuoeasy.test.Orders"/> </session-factory> </hibernate-configuration>
AppTest.java：
package com.shuoeasy.test;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
/**
* Unit test for simple App.
*/
public class AppTest {
Session session;
SessionFactory sf;
@Before
public void init() {
Configuration conf = new Configuration().configure();
ServiceRegistry sr = new StandardServiceRegistryBuilder().applySettings(conf.getProperties()).build();
sf = conf.buildSessionFactory((org.hibernate.service.ServiceRegistry) sr);
session = sf.openSession();
session.beginTransaction();
System.out.println("init");
}
@After
public void destory() {
session.getTransaction().commit();
session.close();
sf.close();
System.out.println("dectory");
}
/**
* 测试是否使用缓存
* hibernate.cfg.xml 加速配置<class-cache usage="read-write" class="com.shuoeasy.test.User"/>
* 使用缓之后出现一条sql，不适用会出现两条sql。
*/
@Test
public void testGet(){
User user1 = (User) session.get(User.class, 1);
System.out.println(user1);
System.out.println(user1.getOrders().size());
System.out.println(user1.getOrders());
session.getTransaction().commit();
session.close();
session = sf.openSession();
session.beginTransaction();
System.out.println("开始第二次查询");
User user2 = (User) session.get(User.class, 1);
System.out.println(user2);
System.out.println(user2.getOrders().size());
System.out.println(user2.getOrders());
}
}
